persistence — any data worthing sending out need to be saved. In fact, every hour the same system sends a refresh snapshot to downstream.

performance penalty of disk write — is handled by innoDB. Most database access is in-memory. Disk write is rare. Enough memory to hold 30GB of data. https://bintanvictor.wordpress.com/2017/05/11/exchange-tickers-and-symbols/ shows how many symbols there across all trading venues.

insert is actually slower than update. But first, system must check if there’s a need to insert or update. If no change, then don’t save the data or send out.

burst / surge — is the main performance headache. We could have a million symbols/messages flooding in